689000 - Fennec discards images in the current viewport and/or too aggressively

Status: RESOLVED DUPLICATE of bug 691169

(Firefox for Android Graveyard :: Panning/Zooming, defect)

Description

[Ralph Giles (:rillian)]

Reading planet.mozilla.org this morning with my shiny new Samsung tablet, I noticed that even when the included images were downloaded, there was a several second delay after scrolling before they display.

This is somewhat reproduceabel with Brendan's blog post:

1. Go to http://brendaneich.com/2011/09/capitoljs-rivertrail/
2. Double-tap to zoom on the content column.
3. Wait for the slide images to finish loading
4. Scroll down slowly, as if you were scanning the post
5. Scroll up quickly, as if you wanted to check something

The text scrolls nicely (well, it's a little jerky, but I think we're still doing better than the native browser) but the images (downscaled png images) are blank for almost two seconds before they display in the context of the surrounding text.

This is a poor experience if the figure was what you wanted to refer back to, and is distracting even when it wasn't.

Comment 1

[Ralph Giles (:rillian)]

This is Gecko/20110921 Fennec/9.0a1 from the nightly channel, running on a Samsung Android GT-P7510 p3 tablet. Installed extensions are Feedback 1.0.1 and Personas 1.0.

Comment 2

[Mark Finkle (:mfinkle) (use needinfo?)]

Could have something to do with decode-on-draw. Fennec is very aggressive about clearing the image cache. The delay could be the decode and redraw.

Comment 3

[Ralph Giles (:rillian)]

Later on I saw currently-visible images disappear-and-redraw-later when scrolling. Maybe it's more noticeable in this instance because the images are scaled down by the <img> tag, so they take up a lot of space and/or there's an extra performance hit if it's redecoding?

Comment 4

[Joe Drew (not getting mail)]

This is definitely decode-on-draw.